COVID-19 has brought home the term “exponential growth” in a gut-wrenching way.
Its spread is an exponential trend that appears on every screen, every day, everywhere in the world. Despite that exponential trend’s profound impact on all humans it remains devilishly deceptive. How could the number of cases explode? Let’s tame COVID-19’s exponential growth in 200 words or less.
We can’t Visualize Exponentials
A simple exponential relationship is y= 2x. When x increases by 1, y doubles.
- Look at your smartphone. Imagining a stack of 15 smartphones is pretty easy (1×15 is linear).
- Imagine 2 smartphones. Imagining doubling that 15 times is impossible. You have to use the smartphone’s calculator to find the total: 32,768 smartphones.
- Humans are awesome at visualizing linear trends but hopeless at exponentials. That’s why we invented calculators.
Small, Exponentially-Growing Events Become Huge, Fast
- Don’t ask “How many?” Ask, “How fast is it doubling?”
- January 23, Hubei, China: 654 COVID-19 cases reported. In America: only 654 cases. Meh. But cases doubled every two days. How soon would that become one billion cases? Yikes! (Answer below.)
- Time from one billion cases to all humanity? 6 days.
- Exponential growth even fooled the New York Times, which warned that while reaching the first million COVID-19 cases took 4 months the second million took only 13 days. The important number to report was the slowing trend: the doublings from two hundred fifty thousand to five hundred thousand to one million took just 6 days.
An exponential trend will look bonkers to your intuition. Trust your smartphone’s calculator instead.
Answer: 654 needs to double just slightly over 20.5 times to surpass 1,000,000,000. If doubling happens every two days, that’s 41 days.